Stimulating low pressure natural gas producing wells

ABSTRACT

Water blockage in subterranean formations, commonly known as water coning, is effectively removed by injecting into the formation a sufficient amount of a micellar solution to contact the area of water blockage. The micellar solution &#39;&#39;&#39;&#39;solubilizes&#39;&#39;&#39;&#39; the water to facilitate the flow of hydrocarbon toward the well bore.

United States Patent Ross [451 Apr. 4, 1972 [54] STIMULATING LOW PRESSURE NATURAL GAS PRODUCING WELLS [72] Inventor: Rupert D. Ross, Robinson, lll.

[73] Assignee: Marathon Oil Company, Findlay, Ohio [22] Filed: Mar. 16, 1970 [2]] Appl. No.: 20,098

Related U.S. Application Data [63] Continuation-impart of Ser. No. 762,129, Sept. 24,

1968, Pat. No. 3,554,288.

2,331,594 10/1943 Blair,.lr ..l66/305UX 2,356,205 8/1944 Blair, Jr. et al. ..252/8.55

2,369,831 2/1945 Jones et al. ..252/8.55

3,254,714 6/1966 Gogal'ty et al. 1 66/274 3,554,288 l/197l Ross 166/305 R Primary Examiner-Stephen J. Novosad Attorney-Joseph C. Herring, Richard C. Willson, Jr. and Jack L. Hummel [57] ABSTRACT Water blockage in subterranean formations, commonly known as water coming, is effectively removed by injecting into the formation a sufficient amount of a micellar solution to contact the area of water blockage. The micellar solution solubilizes" the water to facilitate the flow of hydrocarbon toward the well bore.

14 Claims, No Drawings STIMULATING LOW PRESSURE NATURAL GAS PRODUCING WELLS CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part of my copending application, Ser. No. 762,129, filed Sept. 24, 1968, now US. Pat. No. 3,544,288.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to removal of water blocks in hydrocarbon producing wells, especially gas producers. Micellar dispersions containing hydrocarbon, aqueous medium and petroleum sulfonate are used to remove the water blocks.

2. Description of the Prior Art Water coning around a producing .well can reduce the relative permeability to the flow of hydrocarbon and thus adversely affect the removal of hydrocarbon from a subterranean formation. This adversity is experienced with gas wells wherein water saturation around the immediate area of the well bore is concentrated to effectively reduce the permeability to the flow of gaseous hydrocarbons. In order to effectively remove the water blockage, it is desired that the water be removed and the wettability of the reservoir rock be changed to enhance the movement of hydrocarbon (this term includes gaseous, liquid and fluid hydrocarbons) to the well bore. Thus the relative permeability to the flow of hydrocarbon is improved.

In general, high water saturations around a well bore can be caused by natural ingress of free water saturation from the producing formation or induced by water from drilling fluids, etc., or from casing leaks or various other causes; the result being to increase the saturation of water in the producing formation and thus reduce the relative permeability to the flow of hydrocarbon. The object of this invention is to overcome this reduced relative permeability to the flow of hydrocarbon by removing the water blockage.

Applicant has discovered that by injecting a sufficient amount of a micellar solution to contact the high water saturation in the reservoir rock and permitting the micellar solution to solubilize the water, the adversities of water blockage can be improved. It is postulated that the micellar solution not only solubilizes the water but also wets the rock to make it more permeable to the flow of hydrocarbon than to the flow of water. The term solubilize as used herein defines substantial sorption or substantial emulsification of the water blockage by the micellar solution. The term does not necessarily mean that the water blockage is miscible with the micellar solution.

DESCRIPTION OF THE INVENTION The term micellar dispersion" as used herein is meant to include micellar solutions, microemulsions, transparent emulsions (Blair, Jr. et al., U.S. Pat. No. 2,356,205) and micellar solution technology taught in C. G. Sumner, Claytons The Theory of Emulsions and Their Technical Treatment, th Edition, pp. 315-320 (1954). Examples of useful micellar solutions include those defined in 0.8. Pat. Nos. 3,254,714; 3,275,075, and 3,301,325 to Gogarty et al.; 3,307,628 to Sena; and 3,497,006 to Jones et al. Micellar dispersions differ in many ways from emulsions, e.g., the former are thermodynamically stable systems whereas the latter are not and the former are generally transparent whereas the latter are generally opaque.

Micellar dispersions contain hydrocarbon, aqueous medium, and surfactant. Cosurfactant(s) and/or electrolyte(s) can be incorporated within the micellar dispersion. Examples of volume amounts include about 4 to about 80 percent or more of hydrocarbon, about to about 95 percent aqueous medium, at least about 4 percent surfactant, about 0.01 to about 20 percent cosurfactant (also identified as cosolubilizer and semipolar organic compound) and about 0.001 to about 5 percent or more (weight percent based on aqueous medium) of electrolyte. The micellar dispersion can be oil-external or water-external but preferably is oil-external.

Examples of hydrocarbon include crude oil (both sweet and sour), partially refined fractions of crude oil, and refined fractions of crude oil. Specific examples of hydrocarbon include side cuts from crude columns, crude column overheads, gas oils, kerosene, heavy naphthas, naphthas, straight-run gasoline, liquefied petroleum gases, propane, pentane, heptane, decane, dodecane, cyclohexane, aryl compounds, including benzene, naphthalene, anthracene, and alkylated aryl compounds such as aryl phenols, etc. Preferably, the hydrocarbon is one locally available and can be crude oil characteristic of the reservoir. Also, the hydrocarbon can be unsulfonated hydrocarbon within petroleum sulfonates.

The aqueous medium can be soft, brackish, or brine water. Preferably, the water is soft but it can contain small amounts of salts which are characteristic of the ions within the subterranean formation.

Useful surfactants within the micellar dispersion include nonionic, cationic, and anionic surfactants. Specific examples include those surfactants defined in US Pat. No. 3,497,006 to Jones et al. Preferably, the surfactant is a petroleum sulfonate, also known as alkyl aryl naphthenic sulfonate. The sulfonate can contain monovalent, divalent or higher valency cation(s). Examples of preferred surfactants are petroleum sulfonates having an average equivalent weight within the range of about 350 to about 525, and more preferably about 390 to about 460. The surfactant can be a mixture of two or more low, medium, and high average equivalent weight sulfonates or a mixture of two or more different surfactants. Ammonium and sodium petroleum sulfonates are especially useful.

Cosurfactants useful with the invention include alcohols, amides, amino compounds, esters, aldehydes, ketones, and like materials containing one to about 20 or more carbon atoms. More preferably, the cosurfactant contains about three to about 16 carbon atoms. Specific examples include alcohols such as isopropanol, nand iso-butanol, amyl alcohols such as n-amyl alcohol, 1- and 2-hexanol, etc., alkaryl alcohols such as p-nonyl phenol, alcoholic liquors such as fusel oil, hydroxy compounds, such as Z-butyoxyethanol, and like materials. Preferably, from about 0.1 to about 5 percent of cosurfactant is useful in the dispersion. Mixtures of two or more cosurfactants are also useful.

Electrolytes useful in the micellar dispersion include inorganic acids, inorganic bases, inorganic salts, organic acids, organic bases, and organic salts. Specific examples of electrolytes include sodium hydroxide, sodium chloride, sodium sulfate, hydrochloric acid, sulfuric acid, and those electrolytes found in US. Pat. No. 3,330,343 to Tosch et al. and US. Pat. No. 3,297,084 to Gogarty et al. Little or no electrolyte can be used when the micellar dispersion is designed to have a maximum up-take of brine or connate water, i.e., the dispersion has a capability of solubilizing a large amount of connate water. The electrolyte can be the salts within the aqueous medium.

Where the micellar dispersion is designed to have a maximum affinity for connate water, it may be desired to use a lower average equivalent weight surfactant and/or a lower equivalent weight cosurfactant in an aqueous medium containing little or no electrolyte. Also, the hydrocarbon can be one which is more hydrophilic, these combinations giving a micellar dispersion having a large affinity for brine or an increased uptake for the connate water within the formation. More preferably, the micellar dispersion is designed to be hydrophilic so that a maximum amount of connate water can be taken up or solubilized" by the micellar dispersion.

The micellar dispersion can have a mobility greater than, about equal to, or less than that of the formation fluids within the immediate vicinity of the well bore. Where it is desired to uniformly displace substantially all of the formation fluids away from the well bore, the mobility of the micellar dispersion is about equal to or less than about the mobility of the formation fluids, i.e., combination of interstitial water and hydrocarbon.

The size of the micellar dispersion should be sufficient to completely saturate the rock pores within the immediate vicinity of the well bore that constitutes the water blockage.

Examples of volume amounts include about 1 to about 500 gallons and preferably about 5 to about 250 gallons of micellar dispersion per vertical foot of hydrocarbon-bearing formation, i.e., reservoir rock. Generally, about 25 to about 200 gallons per vertical foot of oil-bearing formation will effectively remove most water blockage.

lt is intended that this invention not be limited by the specific embodiments taught herein. Rather, all equivalents obvious to those skilled in this art are to be interpreted within the scope of the invention.

What is claimed is:

l. A method of removing water blockage from a formation area in the immediate vicinity of a well bore, the method comprising injecting into the formation a sufficient amount of a micellar dispersion, comprised of a petroleum sulfonate having an average equivalent weight within the range of about 350 to about 525, to solubilize sufficient water within the water blockage to increase the relative permeability to the flow of hydrocarbon, and then permitting the hydrocarbon to flow toward the well bore.

2. The method of claim 1 wherein about 1 to about 500 gallons of the micellar dispersion per vertical foot of hydrocarbon-bearing formation are injected into the formation.

3. The method of claim 1 wherein the micellar dispersion is comprised of hydrocarbon, aqueous medium, and cosurfactant.

4. The method of claim 1 wherein the micellar dispersion is designed to have a large affinity for connate water within the formation.

5. The method of claim 1 wherein the hydrocarbon is substantially gaseous.

6. A method of removing water blockage from a hydrocarbon-bearing formation area in the immediate vicinity ofa well bore, the method comprising injecting into the formation about 1 to about 500 gallons per vertical foot of a hydrocarbon-bearing formation of a micellar dispersion comprised of hydrocarbon, petroleum sulfonate having an average equivalent weight within the range of about 350 to about 525, aqueous medium, and cosurfactant to solubilize the water within the water blockage and then permitting the hydrocarbon to flow toward the well bore.

7. The process of claim 6 wherein about 5 to about 250 gallons per vertical foot of hydrocarbon-bearing formation of the micellar dispersion is injected into the formation.

8. The method of claim 6 wherein the petroleum sulfonate has an average equivalent weight within the range of about 390 to about 460.

9. The method of claim 6 wherein the cosurfactant is an alcohol containing about one to about 20 carbon atoms.

10. The method of claim 6 wherein the micellar dispersion is designed to have a high affinity for solubilizing the connate water characteristic of the formation.

11. The method of claim 6 wherein the hydrocarbon within the formation is substantially gaseous.

12. A method of removing water blockage in the immediate vicinity of a well bore penetrating a gaseous hydrocarbonbearing formation, comprising injecting into the formation about 1 to about 500 gallons per vertical foot of hydrocarbonbearing formation of a micellar dispersion comprised of hydrocarbon, petroleum sulfonate having an average equivalent weight within the range of about 350 to about 525, aqueous medium, and cosurfactant to solubilize the water within the water blockage and then permitting the hydrocarbon to flow toward the well bore.

13. The method of claim 12 wherein about 5 to about 250 gallons of the micellar dispersion are injected into the formatron.

14. The method of claim 12 wherein the average equivalent weight of the sulfonate is about 390 to about 460. 

2. The method of claim 1 wherein about 1 to about 500 gallons of the micellar dispersion per vertical foot of hydrocarbon-bearing formation are injected into the formation.
 3. The method of claim 1 wherein the micellar dispersion is comprised of hydrocarbon, aqueous medium, and cosurfactant.
 4. The method of claim 1 wherein the micellar dispersion is designed to have a large affinity for connate water within the formation.
 5. The method of claim 1 wherein the hydrocarbon is substantially gaseous.
 6. A method of removing water blockage from a hydrocarbon-bearing formation area in the immediate vicinity of a well bore, the method comprising injecting into the formation about 1 to about 500 gallons per vertical foot of a hydrocarbon-bearing formation of a micellar dispersion comprised of hydrocarbon, petroleum sulfonate having an average equivalent weight within the range of about 350 to about 525, aqueous medium, and cosurfactant to solubilize the water within the water blockage and then permitting the hydrocarbon to flow toward the well bore.
 7. The process of claim 6 wherein about 5 to about 250 gallons per vertical foot of hydrocarbon-bearing formation of the micellar dispersion is injected into the formation.
 8. The method of claim 6 wherein the petroleum sulfonate has an average equivalent weight within the range Of about 390 to about
 460. 9. The method of claim 6 wherein the cosurfactant is an alcohol containing about one to about 20 carbon atoms.
 10. The method of claim 6 wherein the micellar dispersion is designed to have a high affinity for solubilizing the connate water characteristic of the formation.
 11. The method of claim 6 wherein the hydrocarbon within the formation is substantially gaseous.
 12. A method of removing water blockage in the immediate vicinity of a well bore penetrating a gaseous hydrocarbon-bearing formation, comprising injecting into the formation about 1 to about 500 gallons per vertical foot of hydrocarbon-bearing formation of a micellar dispersion comprised of hydrocarbon, petroleum sulfonate having an average equivalent weight within the range of about 350 to about 525, aqueous medium, and cosurfactant to solubilize the water within the water blockage and then permitting the hydrocarbon to flow toward the well bore.
 13. The method of claim 12 wherein about 5 to about 250 gallons of the micellar dispersion are injected into the formation.
 14. The method of claim 12 wherein the average equivalent weight of the sulfonate is about 390 to about
 460. 